Rebuilding Calpier

[Firewall]

Good Morning,
I'm in the process of rebuilding the rear caliper on my 77 GS750.

The previous owner had done this a few years ago, but I was having an issue with the rear pedal sticking so I decided to rebuild the caliper and master cylinder (I didn't know he had done this until after I had ordered parts). Both were surprisingly clean compared to some of the pics I have seen around here. But then my bikes history hasn't been typical either (always garaged, only 7500 miles).

Anyways, I'm having the hardest time getting the caliper pistons back in. Even with out the seals installed they're very hard to get in. I'm trying to twist them in to place which is what I've seen recommended on here. PO says when he rebuilt it he used "reconditioned" pistons he bought online.

So I guess my question is if this is normal, or if maybe these "reconditioned" pistons are a little out of spec. As clean as the brake system was I'm wondering if this had more to do with the issues I'm having.

Also, are the pistons from Suzuki marked in some way?

Thanks for the help,
Matthew

[7981GS]

Once you get the caliper back together, make certain that you remove the rear brake lever and
remove all of the rust/corrosion on the shaft through the frame and hone out the tube through the frame.
Grease with some synthetic grease after both parts are clean.

Eric

[spyug]

Sounds like they are out of spec. Pistons should be a tight fit but should go in with a bit of firm thumb pressure once lubed with clean brake fluid. No need to resort to clamps or hammers.

I don't recall ever seeing OEM pistons marked in anyway so I guess you wouldn't be able to tell short of ensuring to buy them from an authorized dealer.

I think I'd be going for a new set of OEM pistons but that is likely going to be costly. Having said that though, you really can't put a price on properly working brakes can you?

Good luck with it.
Spyug

[1_v8_merc]

77 gs750

Piston Diameter : Standard - 38.15mm(1.502 inch), Service Limit - 38.18mm(1.501 inch)

Caliper Bore : Standard - 38.18mm(1.503inch), Service Limit - 38.19(1.504inch)


You'll at least need a micrometer.

[Firewall]

Excellent, thanks for the help everyone

[GateKeeper]

Careful on how you do this, you don't want to end up screwing up the seal....

like me....

[daturat100r]

Just bought a piston/seal kit for my gs750 rear caliper ,cost nz$110 from Suzuki,no markings on pistons

[Firewall]

Don't know what I was doing wrong the first half dozen times, but the stars magically aligned and they finally slid in pretty easily.

Once you get the caliper back together, make certain that you remove the rear brake lever and
remove all of the rust/corrosion on the shaft through the frame and hone out the tube through the frame.
Grease with some synthetic grease after both parts are clean.

Eric

This shall forever be a lesson to me about checking the simple things first. While putting it back together I noticed the pedal barely budges without anything else installed. Based on how clean the rest of the system was I'm betting this was the issue all along. Oh well, freshly built brakes are certainly a good thing :-)

Thanks for the help